This application claims the priority of Israel Design Patent Application No. 35626, filed Sep. 16, 2001, titled xe2x80x9cHAND GUARD FOR A SHORT M-16 RIFLE INCLUDING A PICATTINI RAIL FOR MOUNTING ACCESSORIES AND A COVER THEREFORxe2x80x9d.
1. Field of the Invention
This invention is related to the general field of forearm handguards for firearms, and to the particular field of forearm handguards for high rate of fire tactical rifles and carbines such as the M-16/AR-15 family.
2. Background
Tactical shoulder rifles enable rapid high-volume fire that can heat the rifle barrel to very high temperatures. To protect the rifleman against contact with the hot surface, and to help dissipate the heat, the barrel is usually shrouded by a handguard that completely encloses the portion of the barrel directly in front of the receiver over a length sufficient to provide a grip area for the rifleman""s lead hand. This type of forearm handguard is usually xe2x80x9cfree-floatingxe2x80x9d, i.e. connected to the rifle only at end-cap fittings and not directly in contact with the barrel. The handguard thus creates an air space around the barrel to retard heat conduction from the barrel into the handguard. The handguard is vented with air holes or slots to allow heat convection out of the enclosed air space. An early example of this type handguard is described in U.S. Pat. No. 2,965,994. The handguard described in this reference has a laminated construction, comprising a fiberglass-reinforced plastic outer skin laminated to a low-density foam core, with the inner surface covered by a reflecting foil.
Forearm handguards can have a generally triangular or pear-like sectional shape wherein the base is wider and more flat than the top, as in the earlier versions of M-16. This configuration provides a wider support area for the palm when firing offhand, and a more stable platform when firing over a rest, than would a handguard with a narrow bottom. However, there are advantages to a generally cylindrical handguard wherein the top and bottom pieces are identical mating semi-oval half-pieces, such as described in U.S. Pat. Nos. 4,536,982 and 4,663,875. In such handguards, the area at the center of the half pieces (top and bottom of the assembled handguard) is a flat longitudinal rib with a row of vent holes. The exterior of the top and bottom half-pieces described in U.S. Pat. No. 4,536,982 have laterally extending ribs over most of the surface to enhance structural integrity and provide a firm grip, while the flat longitudinal rib has small longitudinal grooves, perhaps to improve the rest characteristic.
It is also known to attach one or more rail adapters to or along a forearm handguard to mount various accessories to the rifle, as described in U.S. Pat. Nos. 5,826,363; 5,590,484 and 5,198,600. When an adapter rail is not being used, it can be protected by covering it with a panel that slides along the grooves at the sides of the rail, as shown in the above U.S. Pat. No. 5,526,363.
An object of the present invention is to provide a lightweight and easily assembled forearm handguard combining several features shown in the above references, with improvements in how the features are interrelated. In particular, the handgrip is made of two injection-molded plastic half-grip pieces, at least one of which has an integrally-molded accessory rail that it is recessed in the area at the center of the half-grip piece. This recessed positioning locates the ribs and guide channel of the rail inside what would be the extended arc of the sides of the half-grip piece in the traditional handguard of this type. A rail cover is provided that replicates the extended arc of the sides of the half-grip piece up to a flat longitudinally extending rib along the center of the cover. Thus, with the cover installed, the grip has essentially the same feel and dimensions as the traditional oval grip as described and shown in U.S. Pat. Nos. 4,536,982 and 4,663,875. Vent holes may be positioned between the opposing ribs of the rail, and the cover may have matching vent holes in registry with the holes between the rails. The half-pieces and rail covers are preferably injection molded in high-density polymer material.
The forearm handguard is made of two half-grip pieces, each half-grip piece being an integral unit that is injection-molded in high-density polymer material. Each half-grip piece is adapted to mate with another half-grip piece to form a top and a bottom of the handguard. Preferably, the half-grip pieces are identical to each other. The two half-grip pieces assemble together to form a handgrip that encloses an air space surrounding a section of the rifle barrel between the receiver and the front-sight/gas return tube assembly.
At least the bottom half-grip piece (both, if they are identical) has an exterior shaped as a generally semi-oval section, curved at the longitudinal sides and having an accessory mounting rail formed in its longitudinal center (corresponding to the bottom of the assembled handguard). The mounting rail has two rows of opposing posts and a guide channel running along and depending under each row (rails of the type are often identified as xe2x80x9cPicatinny Railsxe2x80x9d, although the invention could be used with other rail systems such as the Weaver Rail). The accessory rail is recessed in the area at the center of the half-grip piece. This recessed positioning locates the posts and guide channel of the rail under what would be the extended arc of the sides of the half grip piece. Ventilation holes to the enclosed air space are located in a row in the accessory rail between the opposing post rows.
The rail is open at the front end to allow an accessory to slide onto the guide channels of the rail in the conventional manner, but terminates at the rear end against a raised flat stop with small longitudinal grooves. A preferred type of cover plate for the rail is injection molded of the same plastic material as the half-grip, and has a pair of a rail-engaging flanges that slide along the guide channels of the rail. The flanges may have a flexible rear section with a hook or detent to snap into a depression or latch in the guide channels when the cover is flush to the raised stop. Alternatively, the cover could be made of natural or synthetic rubber and be stretched over the ribs and snap into the guide channels.
The rail cover is formed to replicate the extended arc of the sides of the half-grip up to a flat rib running longitudinally along the center of the cover. The longitudinal sides of the half-grip piece may have laterally extending ribs to provide a grip surface. The cover plate may then have matching lateral ribs at its sides up to the flat rib. A flat raised stop at the rear of the half grip may have matching small longitudinal grooves to complete the feel of the flat rib when cover is installed. The cover plate has ventilation holes in the flat rib that are in registration with the holes between the rail posts in the half piece when the cover is flush to the raised stop.
The half-grip pieces may also be provided with an array of pins or tabs in the interior cavity for the purpose of attaching a metal heat shield to spread the heat evenly over the interior air space. The mounting rings at the front and rear may have a center slot for the gas return tube, and the sides of the rings may extend short of the sides of the half piece, creating a similar slot at the sides to allow the handgrip to be rotated at 90 degree increments around the barrel.